Method of etching titanium diboride

ABSTRACT

A thin film of titanium diboride that has been deposited onto a substrate d patterned using photolithography is dry etched in a commercial plasma etcher with either a chloride, or a mixture of a chloride gas with oxygen, or a mixture of a chloride gas with nitrogen, or a mixture of a chloride gas with a noble gas, or a fluoride gas, or a mixture of a fluoride gas with oxygen, or a mixture of a fluoride gas with nitrogen, or a mixture of a fluoride gas with a noble gas.

The invention described herein may be manufactured, used, and licensedby or for the Government for governmental purposes without the paymentto me of any royalty thereon.

This invention relates in general to a method of etching titaniumdiboride and in particular to a method of dry etching a thin film oftitanium diboride that has been deposited onto a substrate and patternedusing photolithography.

BACKGROUND OF THE INVENTION

Titanium diboride has become of interest in laboratory research becauseof its resistance to change or degradation at high temperatures. It alsoshows promise in acting as a diffusion barrier to other metals.

One of the difficulties involved with working with titanium diboride isthat because of its resistance to attack, it is difficult to pattern. Infact, no wet etches have been available to carry out such patterning.

SUMMARY OF THE INVENTION

The general object of this invention is to provide a method of etchingtitanium diboride. A more particular object of this invention is toprovide a method of etching a thin film of titanium diboride that hasbeen deposited onto a substrate and patterned using photolithography.

It has now been found that the aforementioned objects can be attained byetching titanium diboride with a dry etch.

More particularly, according to the invention, a thin film of titaniumdiboride that has been deposited onto a substrate and patterned usingphotolithography is dry etched by first mounting the substrate bearingthe patterned thin film on the lower electrode of pair of electrodes inthe etch chamber of a commercial plasma etcher or plasma therm etcher.The etch chamber is evacuated to a pressure of about 10⁻⁶ Torr and a dryetchant as, for example, dichlorodifluoromethane (CCl₂ F₂) admitted at aflow rate of about 1 to 100 sccm and a pressure set at about 1 to 500mTorr. An electric field is applied between the electrodes, the powerlevel set at about 50 to 1000 watts and etching allowed to proceed forthe desired time.

Other dry etchants that will etch TiB₂ include a chloride gas, a mixtureof a chloride gas with oxygen, a mixture of a chloride gas withnitrogen, a mixture of a chloride gas with a noble gas, a fluoride gas,a mixture of a fluoride gas with nitrogen, a mixture of a fluoride gaswith oxygen, and a mixture of a fluoride gas with a noble gas.

After the dry etch, the sample is removed and the etch rate determinedby measuring the etch depth and dividing by the etch time.

By adjusting the process parameters, one is able to attain etch rates of5 to 800 Å/min for TiB₂. This is useful for patterning TiB₂ as adiffusion barrier or a Schottky contact to semiconductors.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A thin film of TiB₂ is first deposited on a gallium arsenide substrateby e-beam evaporation and the substrate with thin film of TiB₂ thenpatterned using photolithography.

The substrate bearing the patterned film is then mounted on the lowerelectrode of a pair of electrodes in the etch chamber of a commercialplasma etcher. The etch chamber with the electrodes inside is thenevacuated to a pressure of about 10⁻⁶ Torr. CCl₂ F₂ is then admittedinto the etch chamber at a flow rate of about 2 to 40 sccm and thepressure set at 10 to 200 mTorr. An electric field is applied betweenthe electrodes and the power level set at 150 to 400 watts. The etch isallowed to proceed until the TiB₂ is completely removed in the areasexposed by the photolithography.

Other dry etch processes that can be used to etch TiB₂ include reactiveion beam etching (RIBE), chemically assisted ion beam etching (CAIBE),reactive ion etching (RIE), and magetron ion etching (MIE).

I wish it to be understood that I do not desire to be limited to theexact details as described for obvious modifications will occur to aperson skilled in the art.

What is claimed is:
 1. Method of etching a thin film of titanium diboride that has been deposited onto a substrate and patterned using photolithography, said method including the steps of:(A) mounting a substrate bearing a patterned thin film of titanium diboride on a lower electrode of a pair of electrodes in an etch chamber of a plasma therm etcher, (B) evacuating the etch chamber to a pressure of about 10⁻⁶ Torr, (C) admitting a dry etchant to the etch chamber at a flow rate of about 1 to 100 sccm and a pressure set at about 1 to 500 mTorr, (D) applying an electric field between the pair or electrodes and setting the power level at about 50 to 1000 watts, and (E) allowing the etch to proceed for a preselected time.
 2. Method according to claim 1 wherein the dry etchant is selected from the group consisting of a chloride gas, a mixture of a chloride gas with oxygen, a mixture of chloride gas with nitrogen, a mixture of a chloride gas with noble gas, a fluoride gas, a mixture of a fluoride gas with oxygen, a mixture of a fluoride gas with nitrogen, and a mixture of a fluoride gas with a noble gas.
 3. Method according to claim 2 wherein the dry etchant is a chloride gas.
 4. Method according to claim 3 wherein the dry etchant is dichlorodifluoromethane.
 5. Method according to claim 2 wherein the dry etchant is a mixture of chloride gas with oxygen.
 6. Method according to claim 2 wherein the dry etchant is a mixture of chloride gas with nitrogen.
 7. Method according to claim 2 wherein the dry etchant is a mixture of a chloride gas with a noble gas.
 8. Method according to claim 2 wherein the dry etchant is a fluoride gas.
 9. Method according to claim 2 wherein the dry etchant is a mixture of a fluoride gas with oxygen.
 10. Method according to claim 2 wherein the dry etchant is a mixture of a fluoride gas with nitrogen.
 11. Method according to claim 2 wherein the dry etchant is a mixture of a fluoride gas with a noble gas. 